Radiant energy alarm system



R 2 e332? 9 l 5% m19,v 1943.' M AAUNDSAY 332,154

^ RADIANT'ENERGY ALARM SYSTEM A original Filed April e," 1939 =ae v '/-2 3 INVENTC EA ON BY z. 4M

ATTORNEY 2,332,154 :ADIANT menor ALARM sYsreM Maxwell H. A. Lindsay, Summit, N. J., and Howard J. Pearson, New York, N. Y., assgnors to American District Telegraph Company, Jersey City, J., a corporation of New Jersey Original application April 8, 1939, Serial No.

266,738. Divided and this application .July 27, 1940. Serial No. 347,928

(Cl. Z50-83.3)

14 Claims.

This invention relates generally to burglar alarm systems and apparatus and more particu- )arly to receiving apparatus employing infrared radiant energy. A sensitive detector of radiant energy permits detection of burglars over long distances. Such systems are particularly use ful since a compact apparatus can be used for protecting oices, stores and the like where it is necessaiy that the detection apparatus be easi`v concealed and occupy a minimum amount or space, and where it has previously been necessary to provide extensive wiring and multiple detectors. Furthermore, the radiant energy System is inherently secret and not easily defeated for that reason. Such systems are further advantageous in that they create invisible barriers through which an intruder may penetrate without realizing the existence of any sort of detection system. The radiant energy system also presents the advantage that is capable of viewing and thus protecting large -areaswith the use oi a single transmitter and nceiver whereby very little apparatus and very little wiring is necessary.

This application is a division of the applica'- tion of Maxwell H. A. Lindsay and Howard J. Pearson, Serial No. 256,738, led April 8, 1939.

Radiant energy detection systems are particu- Early useful in outdoor applications such as watcrfronts, prison walls and the like where peculiar problems arise in that weather conditions defeat ordinary apparatus such as that of the photoelectric typo. However, the system or apparatus disclosed herein utilizes radiant energy within that portion of the infrared hand which is capable oi penetrating heavy fogs and even heavy snow storms thus providing protection during all conditions of weather. Heretofore it has been necessary to employ physicai barriers involving the use of extended circuits in protecting large outdoor areas but by means of the infrared beam it is possible to operate a single beam of invisible radiant energy, which. must be penetrated or interrupted by intrudeis',l and thereby create an intangible barrier of great lem-:th with almimmum amount of apparatus.

The principal object ofthis invention is to l provide a burglar alarm system that is capable of viewing and thus sensing or detecting the pres-- ence of a burglar independently er any act of. commission or omission on his part other than his entrance into and natural movements about a forbidden area. or locality.

It is also an object of this invention to provide' a burglar alarm system for viewing an area and thus detecting the presence of a burgl..r by de leo-ting the heat energy given olf or absorbed by his ovm body, or absorbed or reected by objects carried by the intruder as distinguished from so-called beam protection systems involv'- ing the use of a light source or other source of radiant energy. y

Still another object of this invention is to provide a radiant energy detector capable of detecting minute changes in radiant energy over.

to minute quantities of radiant energy and controlling a signal generating apparatus to obtain useful signals.

Another object of this invention is to provide an infrared energy receiver of a rugged construction which is extremely sensitive to heat energy and non-responsive to interfering mechanical vibrations.l

Other objects and advantages of this invention will appear from consideration of the iollowing description taken in connection with the accompanying drawing wherein:

Fig, l is a diagram showing an alarm circuit together with a cross section of a radiant energy detecting unit constructed in accordance with this invention;

Fig. 2 is a top plan section of the detector of Fig. 1 on line 2-'2 of Fig. 1; v

Fig. 3 is a plan view in section of a modification' of the unit shown in Fig. 1;

Fig. 4 is a top plan view of Fig. 3 taken on the section at line v'1--4 of Fig. 3;

Fig. 5 is a cross section of another modification of the detecting unit shown in Fig. 1;

Fig. 6 is an end view of Fig. 5 taken in section on line 6 6;

Fig. 7 shows the appearance of the heat sensitive material when seen under high magnification.

In accordance with the objects of this invention, we provide a radiant energy receiving device of great sensitivity ry using a gas-occludlng substance in a. chamber containing a gas for causing pressure variations therein in response to changes in total energy and byv arranging a .OFFICE-ji i;

tive relation `to said chamber.

.1t is well known from thermodynamic laws .that therelation between the pressure and tem perature of a gasv is expressed by the equation:

` where P is the pressure, V the volume, T the abing theresulting pressure change, would constitute a radiometer. Unfortunately this corr binaticn does not have lsuilicient sensitivityior practical purposes where small quantities "of radiation, such as are emitted by a remote human body, are concerned. 1f, however, a substance is introduced into the cavity which has, first the properly of occluding relatively large quantities of the gas and, second, the ability of discharging the gas and thus raising the pressure a proportionate amount when heat is applied to the substance, a major improvement results. It also follows that a material which expands appreciably when heated will result in still further improvement. Such herein to be disclosed.

The property of occluding gas is termed adsorption and in order that a, material have considerable adsorptive capabilities, it is believed necessary both that the extent of its suriacebe great and that the degree of unsaturation of the surface atoms be high. The rst condition is favored Ly a fie ease in particle size or increase in the volume oi capillaries for a given Weight cf material, and the second, in addition, by the presence o crystal fragments 'and by a decrease in crystal size, so that the atoms which are lesssaturated by their neighbors, such as the corner i atoms, form a greater percentage of the total.

These requirements are met by employing hydrocarbons or soot obtained from the ame of substances are '-2 i 12,832,154 voltage generating element' lor conrerting'presa.v microscope.'` .Onlya lewe separated `fibers are sure changes into variations 1n voltage in operashown, the wool beingemployed inthegdetecting unit in Aa relatively compact form. Thesooted material is then placed wnhinthe gas chamber of the heat detect-ing device where variation in the quantity o infrared energy impinging on the material may cause absorption o r adsorption and evolution of the enveloping gas.

1 pense of installation of alarm systems is reduced burning camphor or of an acetylene lamp. This carbon is very nely divided and therefore has exceptional capability of occluding gas and then evolving the gas again when subjected to radiant energy.' In order to support the finely divided carbon in the most eiective manner, it is deposited on very small bers such as quartz wool, steel wool, glass wool or fine mesh Wire gauze. It has been found that the einciency of the soot in converting radiant energy into pressure en ergy increases as the diameter of the supporting fibers is decreased, and that the extremely nne iibers oijluartz wool offer the best means of support for the soot. In addition, these supporting materials, particularly quartz wool,4 are believed to enhance the response of a radiant energy receiving device of the type referred to above by expanding appreciably under the inuence of received heat energy and causing more pro.4 nounced pressure changes within the gas chamber of the receiving;devi ce.-

The process of sooti'ng the various forms of wool and the wire gauze merely involves holding a small tut of wool or a small piece of gauze in the' name of a camphor or of an acetylene lamp in such a manner that small particles of carbon mentary quartz wool 23 having particles of soot or carbon 23 deposited thereon, as seen through In order for mat-erial'to readily discharge the `adsorbed gas when hea-t is applied, the material or its surface must be capable of absorbing a large proportion of the incident radiation, the thermal capacities must be negligible and the specinc density must be low. that the above mentioned material possesses, in addition to its high adsorptive properties, characteristics which meet these three conditions.

The successful radiant energy receiving device of the type described above must not dissipate 'l the received heat energy thereby depriving the gas occluding substance of any appreciable amount of the received heat energy. Furthermore, the energy converting clement must be of rigid construction and have a minimum amount of electrical leakage since the currents generated are necessarily very small in magnitude and it is iurther necessary to reduce current losses in order to reduce the possibility of false signals or loss of signals. It is also advantageous to utilize a minimum amount of wiring whereby the ex- It is possi-ble to use several diierent converting elements such as the carbon microphone, the

elements lack a sulcient degree of sensitivity to respond eiectively to the minute pressures generated by a gas occluding substance. The condenser microphone, While it is sufficiently sensitive, involved the use of polarizing potentials, is liable to leakages for various reasons and requires the running of heavy multi-wire cables. The piezoelectric crystal microphone is a selfcontained, pressure-responsive, `voltage generating element which overcomes the above mentioned disadvantages and meets the requirements outlined above.

Fig. 1 of the drawing illustrates the application of gas occluding; materials and piezoelectric converting elements to detection of radiant energy within the frequency range which includes visible and invisible heat rays. The convertingunit or radiant energy detecting device includes a heavy metal casing l which serres as a. mechanical protection and also attenuates external pressure waves such as sound which might interfere with reception of the useful radiant energy. The casing l is covered by a cover 3 which includes therein a window E, tbepurpose of which is to admit radiant energy waves of the desired frequency.

A window of rock salt is suitable Where radiant energy in the infrared range of wave lengths between 0.78 micron and 30 microns is transmitted for signaling purposes. Radiant energy in this range is desirable for penetrating atmosphere containing fog, rain or snow.

Between casing l' and cover 3 is located a nonmetallic and heat insulating member 2 having a corneal chamber 4 therein which contains a gas occluding substance 5 of the types described above. It is preferred that a. small tutt of quartz wool, sooted asdescn'bed above, be used as the It is readily seen.

maintaining a constant'pressure on the exterior parts of the crystal. The crystal element 'I composed of two pairs of crystal plates ,I2 and I3 which are separated by insulating members.

I0 to form chamber II. The crystal elements are v supported by thin paper members I5 from the insulating frame 8 which has a passage 9 for connecting the conical chamber 4 with the chamber A l assen substance 5; The casingl has a chamber therein for supporting and protecting the piezoelectric crystal element 'I in any-suitable manner and for deformedV inwardly as in Figs. 3 and 4. Otherwise the operation of this modication and its construction are the same as described above in connection with Fig. 1.

One of the most useful applications of this invention is in the detection of buglaries and it II between the crystal elements I2 and I3. The

space between the paper members I5, the frame 8 and the edges of the plates I2 and I3 is lled with wax. the space between the plates forming a chamber II. The piezoelectric converting element may be constructed in accordance with the general theory and principles as taught by the following patents of Charles B. Sawyer: Nos.

- 1,802,780, 1,802,781, 1,802,782, 1,802,783, 1,803,273, 1,803,274 and 1,803,275. dated April 28, 1931; No.

1.995.257, dated March 19, 1935.

When increased radiant energy is directed through the rock salt window 6, the material 5 expands and discharges gas containedor absorbed therein causing an increase in pressure within the chamber 4. The pressure increase is 'transmitted through the passage 9 in frame 8.

to the chamber I I between the crystal elements I2 and I3. If the radiant energy received by material 5 is decreased, the material contracts and absorbs gas whereby a pressure decrease occurs. The crystal elements are bent or otherwise deformed by all pressure changes whether they be increases or decreases in pressure, the deformation causing generation of voltages in proportion to the amount of pressure change or change'in the received radiant energy. These voltage changes are communicated to a suitable aniplier through the conductors I4, as vshown in Fig. l. the resulting signal being amplified and utilized for alarm purposes or other measurement purposes.'

removes the necessity of extensive wiring as well as being readily installed or removed from the protected premises. The device maybe easily concealed ano consequently is invisible to an intruder who would not know of the presence of a burglar detecting system. In Fig. 1, we show a system -or detecting burglars merely by her-.t given o from or absorbed by the body or any objects which the burglar may be carrying.

The system includes the detector element which may be supported within the enclosure or premises to be protected in such a position that the window Ii views an entire room or any selected zone of an either indoor oroutdoor area.

The detecting unit may be provided with suit- Figs. 3 and 4 show another modification of a detecting unit wherein a. plurality of piezoelec` tric crystal elements 'I are used for converting changes in gas pressure to changes in electrical voltage. The construction of this modification is somewhat similar to that shown in Fig. 1, except that the external casing I includes an elongated chamber 4 which contains the gasoccluding material 5. A large rock salt window 6 is supported at one side of the casing for admitting waves of radiant heat energy. A plurality of piezoelectric crystal elements l are embedded in wax I9 and generate higher potentials than a single unit. The gas-occluding substance' 5 is supported by grid i6 which allows the pressure changes to penetrate spaces Il and bend the crystal elements -l inwardly. The remaining steps in the operation4 of this modification of the invention'are obvious from the description of the unit described in connection with Fig. l.

Figs. 5 and 6 show a further modification of `the detecting unit wherein the piezoelectric element is supported ih a large chamber within the casing I. 'This modication also includes a conical chamber 4 which contains the gas-occluding substance 5. This unit also includes spacers I8 which ll the dead air space surrounding the crystal 'I'. Chamber Il is exaggerated for purposes of illustration but. should be very able lenses or reilectors for eiiiciently collecting `adiant energy from the zone to be protected.

The output of the detecting unit is connected to suitable amplifying apparatus, the output of which operates any form of an alarm device .tuch as a bell which may be located at a central point within the protected premises or at the.

central oilice.

Upon the entry of a burglar into the protected remises, the radiant energy in the form of heat given ofi or absorbed by his body or objects carried by him will cause either increases or decreases in pressure within the detecting unit I2 as described above in connection with Fig. 1. These pressure changes areconverted into electrical impulses which are amplified and operate the alarm device as indicated in Fig. 1.

It will be obvious to those skilled in the art that the radiant energy detectors shown in Figs. l to 6 may also be utilized in conjunction with a source of heat energy for forming a protective beam whereby interruption of the beam of heat energy will decrease the amount of heat received and thereby cause a signal impulse. Such a beam of energy may be arranged to cover or protect any desired area either within an enclosure or within an outdoor premise.

Because ci" the peculiar conditions of the heat reection and absorption which are encountered in different rooms of buildings and in outdoor applications, the radiant energy detecting syslfrom the intruders body. It is alsor possible small. Pressure changes resulting kfrom reception of radiant energy are communicated dithat due to the color of the walls in an enclosure and to the color of the intruders clothing that heat will be absorbed or the reflected heat will be altered when the intruder enters or moves about theenclosure. In the case of the system described and shown in Fig. 1 of the drawing, the detector unit will always detest a change in the amount of heat or radiant energy received by it. In other words, entrance or movement of an intruder is certain to change the amount ci' heat or radiant energy affecting the detecting unit. The same phenomena may occurin systems such as those employing a protective beam of energy and even though the beam of radiant energy is directed intoV the detecting unit it is entirely possible that anintruder may increase /SAL the aniountof. radiant energy in the beam be- ,f

cause of lthe color of his clothing or because of heat reflected' from the walls and again reherent gas adsorbing properties and gas discharging properties of the material in the radiant energy receiver unit. The piezoelectric crystal element follows decreases and increases in gas pressure since any deformation or the crystal element will generate an electrica-l voltage. For the above mentioned reasons the radiant energy receiving apparatus is capable of detecting all changes ofradiant energy within the infrared band which may occur because of movements of a burglar or other intruder.

The above described apparatus has a number of further advantages. Because of the inherent characteristics of the piezo-electric crystal eleinent it is not necessary to provide any energizing or polarizing potentials such as would he necessary in othery forms of microphone elements. It follows that since there are no high potentials or minute discharge currents there will be no electrical leakage present which would necessitate the use of a preamplifier adjacent the detecting unit or heavy multi-Wire cables.

The piezoelectric crystal element also presents 'ie advantage of having no low frequency eutor and therefore it will respcnd'to less than one cycle per second. A

Another advantage o1" the detector element is that it is inherently airtight and mcistureproof whereby changes in humidity and temperature :lo not aect the response characteristics thereof. A further advantage is that the heavy casing surrounding the crystal element attenuates all pressure or other mechanical interfering im-A pulses whereby the occurrence oi false signals is reduced to a minimum.

The radiant energy burglar alarm system presents the inherent advantage that itis unaffected by Weather conditions such asiog, or heavy snow storms or any other changing conditions of the weather. On the contrary, signaling systems such as those employing photoelectric cells are incapable of operating through heavy. fogs and the like since they respond to light energy of short wave lengths in the visible portion of the A spectrum `which does not penetrate fogs. Therefore the system embodying the invention is particularly useful in outdoor applications such as waterfronts, p ison Walls and the like, Where extended areas may be protected with a minimum quantity of apparatus and Wiring. It is also true 'that this system may be used for re detection as well as burglar protection since it is highly sensitive to all radiant energfY variations. Supervision has also been provided so that the system meets all commercial requirements concerning frequent tests of operativ-chess of the system.

This form of detecting system has the added advantage that it prevents false alarms by cornpensating for ambient energy changes such as those caused by local heating apparatus, solar rays, or atmospheric temperature changes because such changes are slow and the electrical circuits associated with the piezoelectric crystal will not respond;

Since there may be any number of variations in adapting this system to a, burglar alarm application or to a rire alarm systemby those skilled in the art, and, as it istapplicable to anyf-kind of signaling system, it isnot desired that this invention shall be limited to the exact embodiments illustrated and described herein, butonly by the extent of the prior art and the appended claiins.`

We claim:

1. In a radiant energy receiver, a housing" member adapted to attenuate sound or other pressure waves, a rock salt windev:1 in sm'd member for admitting radiant energy Waves, a cover plate havinga chamber therein, said chamber being aligned with said Window, a gas-occludi'ng substance responsive to changes of radiant energy within said chamber comprising sooted quartz wool, a pair of piczo-electric crystals separated from each other by insulating elements to form a pressure chamber and supported within said housing member by an insulating frame and a restricted passage through said insulating frame for connecting said chamber to said pressure chamber whereby gas pressure generated by said gas-occluding' substance will deforrn said piezoeicctric crystals to generate an electrical impulse. v

2. In a radiant energy receiver, a housing.

member adapted to attenuate sound `or other pressure waves, a window peiyious to heat energy 'supported in said housing member, a chamber aiigned with said Window and containing mineral wool having deposited thereon a gas-occluding substance, a voltage generating element having a pressure chamber therein and supported within said housing member and a restricted passage Within said housing member for connecting the voltage generating element to the chamber containing the gas-occluding substance whereby gas pressure generated by said gas-occluding substance will cause generation of an electrical impulse.

3. In a radiant energy receiver, a housing member containinga gas-a rock salt window in said member, a plurality of piezo-electric crystal elements within said member, a plurality of chambers between said piezoelectric elements and a heat responsive pressure changing substance in operative relation to said crystal elements whereby changes in radiant energy are converted into electrical energy.

4. In a radiant energy receiver, a housing member, a window in said member which ,is pervious to radiant energy. a series of spaced voltages generating elements Within said member, said elements generating diierent voltages in response to changes mechanical pressure to which said elements are subjected, and a gasoccluding substance in operative relation to said voltage generating elements for applying varying degrees :ff mechanical pressure to said generati-f ing elements whereby cnanges in radiant energy impinging on said substances are converted into electrical energy variations.

5. In a radiant energy receiver, a housing member containing a gas, a Window-in said member for admitting 'radiant energy, ay chamber nicating with said chamber and a piezoelectric crystal element within said expansion chamber for converting changes in pressure to electrical impulses. 6. In a. radiant energy receiver, a housing" member containing a. gas, a window' therein pervious to waves or radiant ener a voltage gentary material t y I 2,332,154 eraiting elementl xrithin said member. a chamber containing a lamentary material which has been sooted ior changing the gas pressurewithin said generating member to convert changes in radiant energy into electrical energy. v

7. In a radiant energy receiver. a housing member, a window pervious .to radiant energy and located-in said housing member for admitting waves of radiant energy. a chamber within said housing member containing a gas-occluding substance comprising a. lamentary material lwhich has been sooted and a second chamber ergy.

8. A radiant energy signaling device compris ing a housing member, a. Window in sa'id housing member pervious to radiant energy, a gas-occluding substance within said member and within the view of said Window, comprising a lamenage generating element cooperating with'said gasoccluding substance for converting pressure changes within said member to electrical impulses. v i

9. In a radiant energy receiver, a housing member, a chamber therein containing a gas, a gas-occluding substance to changes in electrical energy.

10. In a radiant energy receiver, a housing member, a chamber therein containing a gas, a

which has been sooted and a voltelectrical ener '11. Ina radiant energy member, a chamber therein containing a gas, a gas-occluding substance in said chamber comprising sooted steel `wool and means for ccnvertl member containing a gas, and means responsive to changes in radiant energy vious to waves of radiant energy, a voltage generating element Within chamber containing a gas-occluding substance comprising a quantity of an inorganic lamentary material which has been sooted for changing the gas pressure within said chamber, said gas-oc cluding substance being exposed to waves of radiant energy admitted through said window, and

ergy into electrical ener MAXWELL H. A. LINDSAY. HOWARD J. PEARSON.

receiver, a housing and means for converting v said housing member, a 

